JPH04125508A - Position detector and lens device using the same - Google Patents

Abstract

PURPOSE:To improve the precision of the linearity of an output voltage which is led out from an output terminal and to enable higher-precision position detection by applying a voltage to a potential correction point provided at least one place on a resistance body. CONSTITUTION:This detector is provided with terminals 14 and 15 for applying a voltage across the resistance body and a terminal 16 for applying a voltage onto the resistance body 10 except at both its ends. Then power sources 17, 18, and 19 apply voltages to the terminals 14, 15, and 16. The potential correction point is set at a point (c) and the voltage which has an ideal value is applied to the point (c) to correct a deviation in potential. The output value at the point (c) is the theoretical value, so the quantity of the deviation in potential is reduced and the linearity of the output is improved. When the number of potential correction points is increased, the output value approximates the theoretical value, and consequently the precision of the position detection is improved. Thus, the potential correction point is provided at least one place on the resistance body 10 and the voltage is applied to the potential correction point to correct the error in manufacture that a conventional position detector has, thereby enabling the high-precision position detection.

Description

Detailed Description of the Invention Field of the Invention The present invention relates to a position detector that detects the position of a lens using a resistor, a movable body, and a slider, and a lens device using the position detector. .

2. Description of the Related Art A conventional position detection means includes a resistor installed on a base and to which a voltage is applied to both ends, a movable body moving in parallel on the resistor, and a movable body mounted on the movable body, the resistor being mounted on the movable body. There is a method of detecting the lens position using a position detecting means equipped with a slider that slides on the top and picks up the voltage.

The above operation will be explained with reference to FIGS. 3(a) and 3(b).

FIG. 3(a) is a configuration diagram of a position detector in a conventional example.

In Figure 3, 1 is a substrate, 2 is a resistor installed on the cover plate, 3 is a moving body that moves in parallel on the second resistor, and 4 is a moving body that slides on the second resistor and applies a voltage. slider for taking out,
5 is an output terminal, 6.7 is a terminal for applying voltage, 8
is the power source.

If a voltage of E [V] is applied to both ends of the resistor 2 and the slider slides continuously from point a to point b on the resistor, the potential at point a is O [V], The potential at point b can be expressed as E [V]. Therefore, the output voltage is not negative E [V]
a of the slider when outputting a smaller voltage e [V]
The distance X from the point is x=XX assuming that there is no error in the resistance value of the resistor.
---It can be expressed as (1). However, point a,
Let X be the distance between points b.

Problems to be Solved by the Invention However, in actual resistors, the resistance value of the resistor is not uniform due to manufacturing variations, and therefore, the error in the resistance value of the resistor also affects the output voltage taken out from the output terminal. A deviation occurs in linearity. That is, when using a resistor as a position detector, it is extremely important to reduce position detection errors due to errors included in resistance values.

The present invention overcomes the above-mentioned problems by applying a voltage to at least one point on the resistor other than both ends of the resistor to compensate for the deviation in the linearity of the output voltage due to the deviation in the linearity of the resistance value of the resistor. The purpose is to improve the accuracy of the position detector by correcting the

Means for Solving the Problems In order to solve the above problems, a position detector according to the present invention includes at least one sensor formed on a substrate and having both ends to which a voltage is applied.
a movable body that moves parallel to the resistor; a slider that is attached to the movable body and slides on the resistor to extract a voltage; an output terminal attached to the slider; and the resistor. It consists of a potential correction point for applying a voltage provided at at least one location on the resistor other than both ends of the body.

Effects The present invention can improve the accuracy of the linearity of the output voltage taken out from the output terminal with the above-described configuration, and enables more accurate position detection.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, 9 is a substrate for mounting a resistor, 10
is a resistor for extracting position information in the position detection range, 1
1 is a moving body that moves in parallel on the resistor, 12 is a slider that slides in a position detection range on the resistor attached to the resistor, and 13 is taken out from the slider. An output terminal for outputting a voltage; 1415 is a terminal provided to apply a voltage to both ends of the resistor; 16 is a terminal provided on the resistor other than both ends of the resistor for applying a voltage. , 17, 18.19 are terminals 14.15.
This is a power source for applying voltage to 16. Assuming that the range from point a to point b in Fig. 1 is the range in which position detection is performed,
The distance is defined as X, the position of the terminal 16 is defined as point C, and a
The potential at point Ea [v], the potential at point b E
Adjust the power supplies 17 and 18 so that the voltage becomes b [V]. At this time, Eb [V] is larger than Ea [v]. The distance X from the point a where the potential at the output terminal 13 is a [V] can be expressed by equation (1). The case shown in FIG. 4 is shown as an example in which the resistance value of the actual resistor includes an error. In FIG. 4, the actual value is the theoretical value, that is, the case where there is no error in the resistance value, and the broken line shows the actually measured value.

In Figure 4, the actual measured value curve has one extreme value, but of course there are two extreme values.
It is also possible to have one or three.

FIG. 5 shows the result of correcting potential deviation by setting point C in FIG. 4 as a potential correction point and applying a voltage according to the theoretical value to point C.

Since the output value at point C becomes the theoretical value, the amount of potential deviation is reduced and the linearity of the output is improved. Furthermore, if the number of potential correction points is increased, the value will come closer to the theoretical value, and as a result, the accuracy of position detection will improve.

As a second embodiment, a lens device using the position detector of the present invention will be described.

FIG. 2 shows a configuration diagram of a lens device using the position detector of the present invention.

In FIG. 2, 20 is a zoom lens, 21 is a focusing lens, 22.33 is a board for mounting a resistor, 23.34 is a resistor for extracting position information of the position detection range, and 24.35 is a resistor for extracting position information of the position detection range. A movable body that moves in parallel on the resistor; 25. 36 a slider that slides in a position detection range on the resistor mounted on the resistor; 26.
37 is an output terminal for outputting the voltage extracted from the slider, 27, 28, 38, 39 is a terminal provided for applying voltage to both ends of the resistor, and 29 is a terminal other than both ends of the resistor. Terminals for applying voltage provided on the resistor, 30° 31 32, 40.41 are terminals 27
．． This is a power supply for applying voltage to 28, 29, 38, and 39.

A lens device includes a zoom function, and in the past, focusing methods by moving the frontmost lens group of the zoom lens were the mainstream, but in recent years, focusing methods by moving lens groups other than the frontmost group or a part thereof, and focusing methods using image elements. A focusing method based on movement of the lens, that is, a rear focusing method, has emerged.

However, in the rear focus method, the image formation position shifts due to changes in the focal length of the zoom lens due to zooming, which requires correction. Correcting this using a mechanical cam would be extremely complicated, so for example, a zoom position detection means for detecting the position of the lens group used for zooming, and a focusing position detection means for detecting the position of the focusing system. From the obtained position information, a locus of movement of the focusing system is calculated, and a one-dimensional deviation of the focusing system is corrected according to the locus.

(Japanese Unexamined Patent Publication No. 61-73542) FIG. 6 shows the relationship between the zoom position and the amount of positional movement of the focusing system. The ratio of the amount of position movement of the focusing system to the change in zoom position is larger on the telephoto side than on the wide-angle side. (Unexamined Japanese Patent Publication No. 5
7-4018) Therefore, on the wide-angle side, the ratio of the amount of position movement of the focusing system to the change in zoom position is small, so the tolerance for the linearity of the output voltage of the position detector is large. However, since the amount of change is large on the telephoto side, high linearity is required.

In other words, a more accurate position detector is required.

Therefore, with the configuration of the present invention, by providing several potential correction points on the telephoto side, it is possible to realize highly accurate detection of the zoom position on the telephoto side.

Effects of the invention: at least one resistor formed on a substrate to which a voltage is applied to both ends; a movable body that moves parallel to the resistor; and a movable body that is attached to the movable body and slides on the resistor to apply a voltage. A conventional position detector equipped with a slider to be taken out and eight terminals attached to the slider is provided with a potential correction point at at least one location on the resistor other than both ends of the resistor. By applying a voltage to the point, manufacturing errors in conventional position detectors can be corrected, allowing highly accurate position detection. Furthermore, even in the case of a single detector where high linearity is required in a part of the sliding range as shown in the second embodiment, the structure of the present invention eliminates the need for special methods of crushing the resistor such as trimming. This has the excellent effect of achieving high accuracy in some areas.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a position detection device according to the present invention, FIG. 2 is a block diagram of a lens device using a position detector according to the present invention, and FIGS. 3(a) and (b) are diagrams of a position detection device in a conventional example. Block diagram and output characteristic diagram, Part 4 is an output characteristic diagram of a position detector in a conventional example, Figure 5 is an output characteristic diagram of a position detector in the present invention, and Figure 6 is a diagram of zoom position and focusing system in a lens device. FIG. 3 is a characteristic diagram showing a relationship between positional movement amounts. 1, 9.22.33... Board, 2.10.2
3.34...Resistor, 3.11.24.35.
...Moving body, 4.12.2536...Slider, 5.13.26.37...Output terminal, 6
゜7.14.15.27.28.38.39...
・Voltage application terminal, 8, 17. 1B, 19. 3
0. 31. 32. 40. 41...ta
, 6.29... Potential correction terminal, 20...
・Zoom lens, 21...Focusing lens. Agent's name: Patent attorney Akira Odori

Claims (2)

[Claims] (1) At least one resistor formed on a substrate, a movable body that moves parallel to the resistor, a slider that is attached to the resistor and slides on the resistor, and a slider that is attached to the slider. 1. A position detector comprising: an output terminal provided at both ends of the resistor; and potential correction means for applying a voltage to a potential correction point provided at both ends of the resistor and at least one location on the resistor other than both ends. (2) A lens device characterized by using the position detector according to claim (1).